Hard coating layer and method for forming the same

ABSTRACT

The present invention relates to hard coating layer and a method for forming the hard coating layer. A method for forming hard coating layer which comprises: washing a substrate; installing the washed substrate in a vacuum equipment, and vacuating the chamber of the vacuum equipment; cleaning the substrate; forming oblique coating layer on the substrate; and forming vertical coating layer, vertically to the substrate, on the oblique coating layer by applying bias-voltage after forming oblique coating layer is provided. According to present invention, hardness of coating layer may be enhanced by forming a oblique coating layer and vertical coating layer on a substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional Application of U.S. patent applicationSer. No. 13/451,844, which was filed on Apr. 20, 2012, which claimspriority to and the benefit of Korean Patent Application No.10-2011-0145004 filed in the Korean Intellectual Property Office on Dec.28, 2011, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to hard coating layer and method formanufacturing the same, more particularly, the present invention relatesto hard coating layer which has columnar structure and the hard coatinglayer is formed by vertically coating a substrate after obliquelycoating the substrate.

(b) Description of the Related Art

Generally, a method for forming hard coating is a technology thatchanges the composition of coating layer comprised of such as nitrides,carbides and oxides and that improves mechanical properties of thecoating layer by adding heterogeneous materials.

Further, a method for forming nano-sized crystal structure in thecoating layer or a method for forming multi-layered coatings that havedifferent compositions and are in nanometer thickness has recently beenhighlighted.

However, in the above method, there has been a difficulty in coatingprocess and controlling variables in coating process. And thoughhardness of coating layer is enhanced, the coating layer was easilybroken.

SUMMARY OF THE INVENTION

The present invention has been made in an effort to provide hard coatinglayers that the mechanical properties are improved by changing thestructures of the hard coating layers.

According to one embodiment of the invention, a method for forming hardcoating layer which comprises washing a substrate, installing the washedsubstrate in a vacuum equipment, and vacuating the chamber of the vacuumequipment, cleaning the substrate, forming oblique coating layer on thesubstrate, and forming vertical coating layer, vertically to thesubstrate, on the oblique coating layer by applying bias-voltage afterforming oblique coating layer.

In the method according to the invention, the oblique coating layer andthe vertical coating layer are formed in multiple layers.

In the method according to the invention, oblique directions of theoblique coating layer are changed at opposite directions at least twotimes.

In the method according to the invention, the oblique coating layer andthe vertical coating layer are comprised of titanium-nitride (TiN).

In the method according to the invention, the substrate is washed byultra-sonic wave with alcohol and acetone.

In the method according to the invention, the degrees of vacuum in thechamber of the vacuum equipment is equal to or lower than 10⁻⁶ torr.

In the method according to the invention, formation of oblique andvertical coating layer is performed in degrees of vacuum between 2×10⁻²torr and 2×10⁻⁴ torr by injecting argon gas in the vacuum equipment.

In the method according to the invention, oblique angle is between 10°and 80°.

In the method according to the invention, the bias-voltage is appliedbelow 200V.

According to the other embodiment of the invention, hard coating layersthat comprise of an oblique coating layer formed obliquely on asubstrate and a vertical coating layer formed, vertically to thesubstrate, on the oblique coating layer is provided.

In the hard coating layers, the oblique coating layer and the verticalcoating layer are formed in multi-layers.

In the hard coating layers, the oblique coating layer change obliquedirections oppositely at least two times.

In the hard coating layers, the oblique and vertical coating layer iscomprised of titanium-nitride (TiN).

According to the present invention, hardness of coating layer may beenhanced by forming an oblique coating layer and vertical coating layeron a substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of hard coating layer formed on asubstrate according to an exemplary embodiment of the present invention.

FIG. 2 is a graph showing hardness test results of coating layeraccording to structures of hard coating layer according to an exemplaryembodiment of the present invention.

FIG. 3 is a process flowchart for forming hard coating layers on asubstrate according to an exemplary embodiment of the present invention.

FIG. 4 is a schematic diagram of vacuum coating equipment according toan exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed referring to accompanying drawings in order for a personhaving ordinary skill in the art to which said subject matter pertainsto easily carry out the present invention.

As those skilled in the art would realize, the described embodiments maybe modified in various different ways, all without departing from thespirit or scope of the present invention.

Oblique and vertical coating layers on a substrate in an exemplaryembodiment of the present invention improve the hardness of thesubstrate and it will be described referring to FIG. 3 and FIG. 4.

FIG. 3 is a process flowchart for forming hard coating layer accordingto an exemplary embodiment of the present invention, and FIG. 4 is aschematic diagram of vacuum coating equipment according to an exemplaryembodiment of the present invention.

First, before forming coating layer, the substrate 10 is washed (S10),and the washed substrate 10 is installed in a vacuum equipment 100, andthe chamber of the vacuum equipment 100 is vacuated (S20) and thesubstrate 10 is cleansed (S30).

And then, a coating layer is formed on the cleansed substrate 10. Thesubstrate 10 is coated obliquely by rotating a substrate holder 120according to an exemplary embodiment of the present invention.

An oblique coating layer is formed on the substrate 10 by the abovecoating process (S40), and after oblique coating layer 20 is formed,vertical coating layer 30 is formed, vertically to the substrate 10, onthe oblique coating layer 20 by applying bias-voltage.

That is, structures of coating layer are changed by forming the verticalcoating layer 30 on the oblique coating layer 20.

The vertical coating is formed to improve Young's Modulus and hardnessand the oblique coating is formed to improve weakness from brittlenessand not to be easily broken.

The oblique coating layer 20 and the vertical coating layer 30 can beformed in multiple layers, and in particular the oblique coating layerscan be formed with the oblique directions of the oblique coating layersbeing changed in opposite directions at least two times like zigzag or <shapes, the zigzag or < shapes can be obtained by rotating the substrateholder 120 supporting the substrate 10.

The reason why the coating layers 20 and 30 are formed obliquely andvertically is to change the microstructures by applying bias-voltage.The oblique coating layer 20 and the vertical coating layer 30 can beformed over and over at least two times, and the laminatedconfigurations of the oblique coating layer 20 and the vertical coatinglayer 30 are showed in the FIG. 1 and FIG. 2.

FIG. 1 shows hard coating layers formed on a substrate according to anexemplary embodiment of the present invention and FIG. 2 is a graphshowing hardness test results of a plurality of the hard coating layersaccording to an exemplary embodiment of the present invention.

Titanium-nitride (TiN) is used as material for the coating layers in theexemplary embodiment of the present invention, however it is just anexemplary embodiment of the present invention, so zirconium(Zr),titanium-aluminum(TiAl), nitrides and carbides can be used.

The substrate 10 is washed by ultrasonic wave with alcohol and acetonebefore coating process, and the degrees of vacuum in the chamber of thevacuum equipment is maintained at equal to or lower than 10⁻⁶ torrbefore the coating process.

After vacuating the chamber of the vacuum equipment 100, argon gas isprovided into the chamber of the vacuum equipment 100 to make thechamber high vacuum state.

The coating process is performed in the range of 2×10⁻² torr to 2×10⁻⁴torr in the degree of vacuum aspect.

When the degree of vacuum is lower than 2×10⁻² torr, the deposition ratewill be lowered because the metal-ions, generated by arc, are blocked bythe other obstacles like the other ions and cannot arrive at thesubstrate 10. Whereas the degree of vacuum is higher than 2×10⁻⁴torr,plasma or arc cannot be generated because the number of gaseousmolecules is so reduced that the possibility of sputtering is reduced.

In addition, it is desirable that the bias-voltage for forming obliquecoating layer 20 according to the exemplary embodiment of the presentinvention is below 200V. If the bias-voltage exceeds 200V,re-sputtering, that is sputtering not a coating, happens because gaseousions are accelerated toward the substrate.

It is sufficient that the oblique angle a is acute and morespecifically, it is desirable that the size of oblique angle is between10° and 80°.

As the horizontal growth of the said coating layer is suppressed due toshadowing effect, normally coating layer with angle at least 10° isformed, and if the size of oblique angles exceeds 80°, even if obliqueangle of the oblique coating layer 20 is close to vertical angle, thehardness increase of the coating layer is negligible, so the obliqueangle is limited to the above range.

Exemplary embodiments of the present invention are explained morespecifically as below.

In the exemplary embodiments of the present invention, compared withconventional coating layer that coating layer is formed on the substratevertically, oblique coating layer is formed.

The oblique coating layer is used to control the structure of coatinglayer and to form a variety of coating structure of coating layer.

The structures that can be made by oblique coating are such as, zigzag,spiral, oblique cylinder and the structures made by oblique coating canbe applied to gas sensors due to large specific areas compared toconventional coating layer.

The structure of the exemplary embodiment of the present invention isnot the same with the said structure but is close to oblique columnarstructure.

The physical properties of coating layer can be changed from thestructural changes of the coating layer and the formation ofmulti-layered coating.

The exemplary embodiment of the present invention comprises of processfor forming coating layer by structure design of hard coating layer andvacuum coating method. The material for the substrate 10 of theexemplary embodiment of the present invention is stainless steel.

After the substrate 10 is washed by ultra-sonic wave with alcohol andacetone, the substrate 10 is installed in a vacuum equipment 100 and thevacuum equipment 100 was vacuated in 10⁻⁶ torr with turbo molecular pump(TMP) 150 and rotary vane pump (RVP) 160.

When degree of vacuum is in 7×10⁻⁴ torr by providing argon gas (Ar) intothe vacuum equipment 100 after vacuating the vacuum equipment 100,cleaning the substrate 10 is performed by applying about 400V into thesubstrate 10 from arc generated by applying direct current (DC) to anodearc source 130 that titanium target 140 is installed.

When cleansing the substrate 10 is finished, titanium-nitride coatinglayer is formed by providing argon gas together with nitrogen gas at thesame pressure when the substrate is cleansed.

When forming a titanium-nitride (TiN) coating layer, coating isconducted by rotating the substrate holder 120 in order to the substrate10 and the anode arc source 130 is in oblique angle instead of verticalangle. The oblique angle is 45°.

When a desired thickness for oblique coating is finished, a top coatinglayer is formed by applying electric field about 100V into the substrate10 while the substrate holder 120 is tilted.

The process for forming coating is finished when a desired thickness ofthe top layer is accomplished.

In the exemplary embodiment of the present invention, coating layerswith a variety of coating shapes were formed as shown in FIG. 2, thehardness of comparative example that only vertical coating layer 30 wasformed on the substrate was 26 GPa, while the hardness of sample No. 4that vertical coating layer was formed after oblique coating layer wasformed in zigzag was 34 GPa.

Further, when oblique coating layer 20 and vertical coating layer 30were formed repeatedly by two times (sample No. 6), the hardness of thecoating layer exceeded 30 GPa.

Compared to sample No. 2 that oblique and vertical coating layer isformed at once respectively, the hardness of sample No. 6 that obliqueand vertical coating layer is formed twice is enhanced.

Generally, the hardness of titanium-nitride can't exceed 30 GPa, thehardness of coating layer that formed in the exemplary embodiment of thepresent invention can exceed 30 GPa.

The exemplary embodiments of the present invention make coating layergrows vertically with regard to the substrate 10 by applying electricfiled into the substrate 10 while forming oblique coating layer on thesubstrate 10 by tilting the substrate 10.

Coating layers with a variety of coating shapes may be formed with theaid of oblique coating and electric field. Hardness of hard coatinglayer is highly enhanced by forming vertical coating layer on theoblique coating layer with electric field after forming oblique coatinglayer on the substrate 10.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments.

On the contrary, it is intended to cover various modifications andequivalent arrangements included within the spirit and scope of theappended claims.

What is claimed is:
 1. A method for forming hard coating layer whichcomprises: washing a substrate; installing the washed substrate in avacuum equipment, and vacuating the chamber of the vacuum equipment;cleaning the substrate; forming oblique coating layer on the substrate;and forming vertical coating layer, vertically to the substrate, on theoblique coating layer by applying bias-voltage after forming obliquecoating layer.
 2. The method of claim 1, wherein the oblique coatinglayer and the vertical coating layer are formed in multiple layers. 3.The method of claim 1, wherein oblique directions of the oblique coatinglayer are changed at opposite directions at least two times.
 4. Themethod of claim 1, wherein the oblique coating layer and the verticalcoating layer are comprised of titanium-nitride (TiN).
 5. The method ofclaim 1, wherein the substrate is washed by ultra-sonic wave withalcohol and acetone.
 6. The method of claim 1, wherein the degrees ofvacuum in the chamber of the vacuum equipment is equal to or lower than10⁻⁶ torr.
 7. The method of claim 1, wherein formation of oblique andvertical coating layer is performed in degrees of vacuum between 2×10⁻²torr and 2×10⁻⁴ torr by injecting argon gas in the vacuum equipment. 8.The method of claim 1, wherein oblique angle is between 10° and 80°. 9.The method of claim 1, wherein the bias-voltage is applied below 200V.